This proposal seeks funds to investigate the significance of the preliminary observation that Cytochalasin B inhibits in vitro ovulation in the frog and a hormone-induced movement of follicle cells in the starfish ovary which is probably related to spawning. Since the source of the energy which moves an egg out of an ovary is not known for any species, and since this process(es) is/are of great significance in mammals, for studies of fertilization control in particular and in reproductive physiology in general, the applicants wish to explore the possibilities suggested by this observation. Several authors have associated cytochalasin sensitivity with an intra-cellular, microfilament-mediated contractile system. The mode of action of cytochalasin B is not yet understood, but the applicants feel that an ultrastructural evaluation of follicle cell sensitivity to cytochalasin is a logical first step in the analysis of this problem. This proposal seeks support for such an evaluation, and for further studies on ovulation and spawning to further clarify the responses of these processes to cytochalasin. Transmission electron microscopy will be used, and all populations of filaments and microtubules observed in the three cell layers of the amphibian follicle, and the single cell layer around the starfish oocyte, will be investigated with respect to their sensitivity to the presence of ovarian hormones (progesterone?; 1-methyl adenine), colchicine and cytochalasin B. In this way the roles played by these organelles in ovulation, if any, will be revealed, and further elucidation of maturing oocyte release will become possible.